JPMorgan’s disclosure stated that user contact information such as “name, address, phone number and email address” had been compromised for online banking users who had logged in to chase.com or jpmorgan.com from any device.

While the bank also noted that fraud rates have remained at normal levels since the breach, the loss of contact information increases the risk of identity theft for millions of Americans.

At a minimum, Americans affected by the breach can now be targeted in email phishing attacks. An example of phishing would be a scammer sending an email pretending to be from Chase, asking to “verify” (aka steal) a person’s account information and online banking password.

The fact that hackers were able to make off with such a huge amount of data calls into question the safety of more sensitive data like social security numbers, dates of birth and passwords.

That’s a scary thought. And yet another reason why it might be time to go back to stashing cash under your mattress.

Chris heads up interactive content and data visualization at Mic. Previously he blogged about data visualization while traveling around India, and before that he worked on big data applications at Palantir Technologies. Chris grew up in the SF Bay Area and graduated from Stanford. In his free time he's training for a marathon and trying to become a better cook.